The Clinical Core will implement and manage the human subjects research for the PPG Projects. Centralizing the human subjects research activities for all projects of the Center will save effort and cost by consolidating the necessary personnel, facilities, and resources. The Clinical Core investigator and personnel have a successful track record with similar multi-project clinical research protocols for over a decade. The Clinical Core approach has been validated by preliminary studies with the investigators in this proposal. Aim 1: Recruit, enroll, and retain study subjects. The clinical research protocol will consist of a longitudinal, prospective study of exacerbation-prone asthmatic children (n=100) and cross- sectional biosampling of three control groups: 1) mild, exacerbation-resistant asthmatic children (n=100); 2) non-asthmatic, atopic children (n=50); and 3) non-asthmatic, non-atopic children (n=50). These control groups will be used to characterize the spectrum of airway, CD4+ T cell, and surfactant responses that are not involved in exacerbations. Participants will be identified for recruitment through IRB-approved means using recruitment databases, electronic medical records, and public, clinic, and hospital advertisements. Potential participants will be screened with a questionnaire that collects contact information and inclusion and exclusion criteria. Regarding longitudinal follow-up of the exacerbation-prone group, the Clinical Core team has a strong history of enrollment, recruitment, and >90% participant retention in longitudinal studies of urban children with asthma. Aim 2: Perform clinical characterization of participants through asthma and atopy phenotyping and biosampling of study subjects. Phenotyping will include a determination of asthma, atopic status, exacerbations, and asthma severity. Biosamples will include induced sputum, nasal brush, nasal mucus, blood, and urine. Aim 3: Provide data and sample management. The Clinical Core will provide biosample tracking, routing, preparation and testing, and will provide de-identified data to the Projects and the Biostatistics, Bioinformatics and Environmental Sampling Core. Phenotyping data will be entered into a HIPPA-compliant, IRB-approved REDCap (Research Electronic Data Capture) database (NIH/NCATS Colorado CTSI Grant Number UL1 TR001082).